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  <h1 class="title">简介</h1>
  <p class="para">
<acronym title="PHP: Hypertext Preprocessor">PHP</acronym> Judy is a <acronym title="PHP Extension and Application Repository">PECL</acronym> extension for the 
<a href="http://judy.sourceforge.net" class="link external">&raquo;&nbsp;Judy C library</a> 
implementing dynamic sparse arrays.
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   <p class="para">
A Judy array is a complex but very fast associative array data structure for 
storing and looking up values using integer or string keys. Unlike normal 
arrays, Judy arrays may be sparse; that is, they may have large ranges of 
unassigned indices.
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   <p class="para">
A Judy array consumes memory only when populated yet can grow to take advantage 
of all available memory.  Judy&#039;s key benefits are:  scalability, performance, 
memory efficiency, and ease of use. Judy arrays are designed to grow without 
tuning into the peta-element range, scaling near O(log-base-256) -- 1 more RAM 
access at 256 X population.
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